Real time data smoother and significant values selector

Abstract

A digital data preprocessor is disclosed wherein consecutive samples of noisy raw digital data telemetered from a dropsonde and decommutated are stored in a first storage stack of registers. Adjacent samples are subtracted, the adjacent first-differences therefrom are subtracted, and the resulting second-differences are stored in a second storage stack of registers. By a comparison of raw data with the second-differences, raw data distorted by noise are measured and subsequently restored to a new value calculated from valid values of raw data samples adjacent to the distorted value. The second-differences are fed through a series of adders to provide a sequence of second-sliding-sums which are stored in a third stack of storage registers. A significant value selector tests the sliding-sums using three different criteria. The results of the tests are used as a basis for selecting raw data samples from the stack for pre-output smoothing of the raw data. The pre-output smoothing and value selection allow for a reduction in the number of data points fed to a processor such as a refraction calculator.

What is claimed is: 
     
       1. An apparatus for distortion detection, data restoration and smoothing, and significant value selection for a discrete number of consecutive samples of real time digital data, comprising in combination: first storage means formed to be connected to receive the samples for providing a first signal of consecutive first-differences of a plurality of the last received samples, a second signal (A) of a plurality of intermediate received samples, a third signal (D) of a plurality of the first received samples, and a ready signal indicative that said first storage means has received the samples;   second storage means connected to receive the first signal for providing a fourth signal of a plurality of last consecutive second-differences and a fifth signal of consecutive first-sliding-sums of a plurality of first consecutive second-differences;   restorer means connected to receive the second signal (A) and the fourth signal for providing to said first storage means a sixth signal (B) of a plurality of samples restored therein and strobe pulses, and to said second storage means a seventh signal (C) of a plurality of clear pulses;   third storage means connected to receive the fifth signal for providing an eighth signal of a plurality of consecutive second-sliding-sums;   selector means connected to receive the eighth signal and the third signal (D) for providing consecutive smoothed, restored samples; and   control means connected to receive the ready signal for providing control signals to control said first storage means, second storage means, restorer means, third storage means, and selector means.   
     
     
       2. The apparatus of claim 1 wherein said first storage means comprises: a plurality of first shift registers connected in series for providing temporary storage and shifting of consecutive samples therethrough, also providing the last samples fifteen and sixteen, the intermediate samples seven through fifteen inclusive, and the first samples one, two and three therefrom, and for receiving restored data for substitution of intermediate samples that are distorted; and   a first subtractor connected to receive the last samples for providing the first signal therefrom.   
     
     
       3. The apparatus of claim 1 wherein said second storage means comprises: second difference means connected to receive the first signal for providing differences thereof;   a plurality of second shift registers connected in series for providing temporary storage and shifting of consecutive differences of the first signal, providing the fourth signal therefrom and receiving the seventh signal; and   a first adder connected to receive the fourth signal from the last four of said second registers for providing the fifth signal.   
     
     
       4. The apparatus of claim 1 wherein said restorer means comprises: a selectable binary divider connected to receive one of a plurality of the second signal (A) for providing a reference signal (R);   comparator means connected to compare the fourth signals and the reference signal (R) for providing a signal therefrom indicative of excessive second differences;   set membership determiner means connected to receive said comparator means output signal for providing a signal therefrom indicative of members of a set of excessive second differences;   distortion verifier means connected to receive said set membership determiner means output signal, said comparator means output signal and the fourth signal for providing a signal (Z) indicative of distortion of the samples;   set size storer means connected to receive said set membership determiner means output signal and said distortion verifier signal (Z) for providing temporary storage and output of said determiner's output signal; and   restorer means connected to receive said set size storer means output signal and the second signal (A) for providing the sixth and seventh signals (B and C).   
     
     
       5. The apparatus of claim 1 wherein said third storage means comprises: a plurality of third shift registers connected in series for providing temporary storage and shifting of consecutive fifth signal therethrough and therefrom;   a second adder connected to receive the fifth signal from said third shift register for providing the sum thereof; and   a plurality of fourth shift registers connected in series for providing temporary storage and shifting of consecutive eighth signals and output thereof.   
     
     
       6. The apparatus of claim 1 wherein said selector means comprises: averager means connected to receive the third signal (D) and one of the plurality of eighth signals for providing a smoothed data signal;   peak selector means for providing a signal indicating when a preselected peak threashold has been exceeded by at least one of the eighth signals and also for providing a signal indicating when the peak threshold will be exceeded during a succeeding time increment;   cumulative selector means for providing a signal indicating when both a preselected cumulative shift threshold has been exceeded by the third storage means and a preselected cumulative second-sliding-sum threshold has been exceeded;   force selector means for providing a signal indicating when the total number of shifting operations in the third storage means exceeds a preselected force threshold; and   gating means connected to receive the signals from said peak selector means, said cumulative selector means, said force selector means, and the smoothed data signal from said averager means, for outputting said smoothed data signal whenever one of the peak selector, cumulative detector, or force selector signals are present.